I had no negative impacts of the Z1, I think it is just some sort of ground nut or similar natural product? If you manage to get hold of it I would use it for a few treatments as snails are bigger so it may take longer, but it is just a apply once treatment so really easy to do!
I did have a quick search whether it is available and I also did't find any in Australia??? You may be able to get some from abroad maybe but I don't know whether you can import it??? It may not kill them anyway?
This is the link to the manufacturers website,
http://www.sl-aqua.com/en/conditioner/products_z1.html
That doesn't leave many options does it? Putting food in is what I do when I want to clear mine, just leave it an hour and it will have good results. I have actually done this in the shrimp tank, sort of by accident, I put spinach in for the shrimp but they weren't interested, but it got covered with detritus worms, so I carefully remove the leaves next morning and a load of worms with them - result?
Simon
edit - I looked at the Z1 I have but it only lists ingredients as 'plant extracts'?